The present invention relates generally to fuel injection systems for internal combustion engines, and more particularly to, a method and apparatus for obtaining and installing fuel injector data that is specific to a particular fuel injector in an engine controller.
In U.S. Pat. No. 6,360,161 of Francis et al., there is shown and described a method and system for fuel injector coefficient installation. In that patent, there is a method and system that allows the use of less precisely manufactured fuel injectors to be used in engines while still achieving the optimum of performance by insuring that each individual injector deliver a predetermined pulse width of fuel.
The advanced fuel injectors used today are defined by a third-order polynomial and, therefore, in accordance with the Francis et al. patent, the coefficients for the third order polynomial are individually obtained for each fuel injector and those coefficients are stored in a read/write memory. That data representative of the coefficients is eventually introduced into the memory of an ECU within the engine in order to achieve the desirability that each injector deliver approximately the same quantity of fuel, in approximately the same timed relationship to the engine for proper operation.
Accordingly, in the aforementioned Francis et al. patent, the inventive method and system relate, in part, to replacing the fuel injector coefficient data in an ECU of a fuel injected engine. The method and system involve obtaining and storing coefficient data that is specific to a particular fuel injector, and providing that coefficient data, together with the associated fuel injector, to a customer for replacement in an engine.
A computer program was also supplied to read out the existing coefficient data from the ECU before writing the replacement coefficient data so that restoration of the existing coefficient data, and the associated fuel injector, can be accomplished if the replacement fuel injector does not correct the service problem experienced. The system includes a log file to prevent misuse of the coefficient data by tracking how the program and data are used. That is, once the replacement coefficient data is used, the only way to reuse the data is if the original existing coefficient data is restored in the ECU from which it originated. If the data is restored, and it is assumed that the original fuel injector is reinstalled in the original cylinder from which it came, the program allows the reuse of the replacement coefficient data.
While the aforementioned method and system of the Francis et al. patent is sufficient to insure that the coefficients are input into the memory of the ECU in order to determine the third order polynomial function of each individual fuel injector, and therefore that the individual fuel injector is able to accurately inject the pulse width of fuel into the cylinder, there is an additional bit of information or data that is also necessary to the proper functioning of the engine and which is related to the timing of the fuel injection into the cylinder.
It is, of course, also well known that the timing of that introduction of the injected fuel into the cylinder is critical to the performance of the engine and that timing function was also illustrated in the aforedescribed Francis et al. patent. The timing of the injected fuel changes with RPM of the engine, that is, at slow speeds the injection of fuel is quite close to the timing ignition pulses while, at higher RPM, the fuel pulses are considerably in advance of the timing ignition pulses. The fuel injector delivers the pulse or injection of fuel after being activated by an electrical signal that is controlled by the ECU of the engine. A problem, however, exists in the timing of the actual delivery of fuel from an injector after the injector has received an electrical signal activating the injector. Thus, while timing ignition pulses can be quite accurate, the actual introduction of the fuel from a fuel injector after the injector has received the electrical signal to inject the fuel is not as accurate, and depends on the particular characteristic of the fuel injector, and all fuel injectors may have some differences in actual delivery time of the pulse of fuel after being activated by the electrical signal to the fuel injector.
As can now be understood, the time of the actual injection of fuel into the cylinder is critical to the performance of the engine, however, that pulse of fuel is not injected at the time the injector receives the electrical signal activating the fuel injector. Instead, there is a time delay between the time that the electrical signal reaches the fuel injector and the actual delivery of a pulse of fuel by that injector, and that delay is due to the need for pressure to build up in the fuel injector before the actual pulse of fuel is delivered.
Accordingly, in order to achieve the desired performance of the engine, it is necessary for the data or information relating to the time delay of a fuel injector to be present in the ECU so that the ECU can know how far in advance the electrical signal must be transmitted to the fuel injector in order to inject the fuel at the precise desired time into the cylinder.
At the present, the time delay that is utilized in determine the timing of the electrical signal to activate a fuel injector is taken as an average value and therefore each injector must be constructed with relatively tight tolerances in order to make that average delay time a valid bit of data to be used in the engine to determine the timing of the pulse of fuel. It would, therefore, be advantageous to be able to have the exact time delay for a particular fuel injector and use that actual data so as to allow greater tolerances in the manufacturing of fuel injectors, and therefore lower costs, while still maintaining the accuracy of the precise time the fuel is injected into a cylinder.